The creation of an ostomy (stoma) is the therapy for many sufferers of diseases or injury of the gastrointestinal or urinary tract. An ostomy is the rerouting of the tract through the abdominal wall to outside the patient's body. Once a stoma has been created, the patient must, usually for the rest of his or her life, use a device worn on the body for capturing or containing the body waste. This has traditionally been done with a bag or pouch attached to the body with adhesive patches or constricting belts. However, the wearing of such a pouch can be an extremely embarrassing and belittling experience for many ostomates. A pouch requires significant changes in a person's public and personal activities.
A controlled evacuation appliance offers the potential for an ostomate to return to some form of normality. The appliance is used to block the stoma mouth, in order to store the liquid and/or solid stool temporarily inside the tract. The appliance is deactivatable and/or removable manually when the ostomate desires to discharge the stool from the stoma. A design feature which distinguishes a controlled evacuation appliance from a conventional ostomy pouch is the presence of a stoma seal, for blocking the stoma mouth.
U.S. Pat. No. 4,950,223 describes a controlled evacuation appliance in the form of an inflatable ostomy plug. The plug includes a stoma seal in the form of an inflatable bung which fits inside the stoma. In use, the ostomate can inflate the bung to plug the stoma, by compressing a bellows pump located externally on the plug. The bung is deflated by an opposite movement of the bellows. Although this example of an inflatable plug is highly appealing in theory, it suffers from certain impracticalities. In particular, it is not possible to vent flatus while the bung is inflated in the stoma. Flatus can only be vented when the bung is collapsed to allow discharge of body waste from the stoma. This presents severe limitations for the ostomate, because the ostomate will have to collapse the bung very frequently in order to avoid an uncomfortable accumulation of flatus within the body.
The venting of flatus for a controlled evacuation device remains a significant problem. It is technically difficult to provide a controlled evacuation appliance that can achieve a reliable seal in use to block escape of stool while allowing flatus to vent through or around the seal.
Flatus vents are known from the field of ostomy pouches. However, in a pouch, there is no equivalent stoma seal that has to withstand prolonged contact with stool. Also, in a pouch, the flatus is able to separate easily from the stool because the stool drops under gravity into the collection region of the pouch. The vent arrangements for pouches are designed to withstand only occasional (accidental) contact with stool, and do not perform reliably if exposed to prolonged contact with stool, especially in direct contact with the stoma.